The invention described herein includes the use of a transparent LCD glass panel as one of the panes in a three-pane unit, such as one used in an insulated glass refrigerator/freezer door.
One of the issues with such a door is supplying power, data and/or communications to the components within the refrigerated display case. Glass refrigerator/freezer doors commonly have a mechanism to supply 120VAC or 240VAC power to the door for anti-sweat heaters. Most stores use a traditional electrical cord. This cord flexes in the cold and suffers from copper conductor fatigue, and insulation cracking. To overcome these weaknesses, solutions have been provided in which the electrical conductors are passed through the hinge pin. By running the conductors concentric with the axis of the hinge pin, flexing and fatigue is minimized, thus improving reliability. The high voltage conductors and associated contacts require appropriate insulation and spacing as dictated by UL and other safety certification organizations. See, for example, U.S. Pat. No. 4,671,582 (referred to herein as the “'582 patent”), issued on Jun. 9, 1987 to Stromquist, et al., the entirety of which is incorporated herein by reference.
Other types of refrigerator/freezer doors also require both power and data. For example, LED light fixtures mounted to the swinging door, LED illuminated marquee signs mounted inside the insulated glass assembly of the door, LCD displays mounted on the door handle, and transparent LCD glass panels with advertising all require both power and data. Most of these products require UL Class 2 low voltage (<60VDC), and many require a data supply, e.g. LCD displays with advertising pictures or videos requiring TCP/IP type data communications.
The problem to be overcome is how to provide the DC power and data communications to these devices. Running all the conductors through the prior art electrical hinge pin is difficult due to space limitations. Running all the conductors in a traditional cable suffers from the aforementioned reliability issues with flexing in the cold. Batteries for DC power are a maintenance concern. Transforming the AC power available in the door for anti-sweat heaters requires bulky transformers and capacitors which are difficult to fit into the narrow door rails.